Hydraulic systems based on adjustable pumps, proportional electrohydraulic equipment and controllers are used in mobile machines. The authors propose a new scheme of the hydraulic system for mobile machines, which provides the auger drilling operation. A number of studies have shown that a certain ratio should be maintained between the frequency of auger rotation and its feed during operation, where the productivity of soil disruption should not exceed the productivity of transporting loose soil from the drilling zone. Ensuring the required ratio between the speed of the auger rotation and its feed is implemented by a controller that works according to a certain algorithm. A nonlinear mathematical model of the hydraulic system was developed to create the algorithm for controller operation and setting. The equations of the mathematical model are solved in the MATLAB-Simulink environment by the Rosenbrock method. As a result of solving the equations for the mathematical model, the dependences of variables describing the state of the hydraulic system on time are obtained. The values of the controller settings are determined at which the hydraulic system works steadily, the error of flow rate stabilization, the time for pressure adjustment and readjustment does not exceed the allowable values. The algorithm for controlling the auger feed value is formed. This algorithm provides the necessary ratio between the auger feed and speed, as well as reducing the feed rate in the case of soil hardness increases. This creates the conditions for uninterrupted pit drilling at full depth and protection of the hydraulic system from overload.

Mobile machine hydraulic circuits tend to adopt electrohydraulics. Such hydraulic circuits are based on controlled pumps, modulated hydraulics, sensors and controllers. This allows adapting the hydraulic circuit operating modes to the changes of external conditions of the machine operation. Application of hydraulic circuits with electrohydraulics in mobile machines allows to use mobile machines efficiently with a high number of removable endangers, increases their performance and improves the quality of performed works. The authors propose an adaptive hydraulic circuit for a mobile machine. The operation process in the adaptive hydraulic circuit in static and dynamic modes is determined by the interaction of the pump controller and pressure differential control valves. The hydraulic system operation stability, its fast response and readjustment are determined by the controller parameters. It has been revealed that the main parameters affecting the dynamic characteristics of the hydraulic system are: throttle area and coefficient of amplifying the pump controller orifice, dampener area and coefficient of amplifying the pressure differential control valve orifice. These parameters affect the stability, controlling and readjustment time in the hydraulic circuit differently. A functional including the values of controlling time , σ controlling and losses in the pump controller was used as an optimization criterion. The optimization has been made according to the developed mathematical model applying the method developed by I. Sobol and R. Statnikov. During the optimization each controller parameter changed on 3 levels. 81 tests were made and the best combination of controller parameters for the optimization criterion was determined. The following hydraulic circuit operation values were reached under the optimal values of parameters = 1.0·10-6 m2, = 1.0·10-3 m, = 1.2·10-6 m2, = 10·10-3 m: = 1.1 с, σ = 32 %, = 0.82 kW that comply with the requirements towards hydraulic circuits of mobile machines.

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